To protect facilities such as a telephone switching office or computer installation from fire or from failure as a result of over-temperature conditions, temperature sensors generally are installed at the facilities to generate alarm signals in response to excessive temperatures. The alarm signals are transmitted to a remote control center which may contain an electronic switching system (ESS) wherein telephone office personnel monitor cathode ray tube displays to determine temperature and other conditions at each facility. In response to excessive temperature at a particular facility, the cathode ray tube is controlled by software to indicate the existence of the condition, its location and how to take corrective action.
Prior art alarm systems of this type of which we are aware have two inherent deficiencies. First, the system itself is prone to failure as a result of a failure of a temperature sensor at the facility monitored or a failure in the link for transmitting an alarm signal from the facility to the control center. Second, the display at the control center develops a single alarm message on the cathode ray tube in response to an over-temperature condition. The message, however, may be overlooked or ignored by attending personnel and the alarm accordingly unheeded. A need therefore exists to provide fail-safe monitoring of temperature and transmission of temperature alarm data to a control center and to periodically repeat over-temperature alarm signals until responsive action is taken.